<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Document</title>
</head>

<body>
  <div id="app">
    <p :style="{opacity,color:" green",font-size:40px}">style</p>
    opacity: <input type="text" v-model="opacity">
  </div>
  <script src="./js/vue.js"></script>
  <script>
    const vm = new Vue({
      data: {
        opacity: 1
      },
    });
    vm.$mount();
  </script>
</body>

</html>